When a personal computer is switched on, the BIOS, which is a program stored in an erasable programmable read only memory (EPROM) in the hardware of the system, carries out a sequence of operations                it determines the system configuration,        it verifies some of the hardware        it then loads the OS loader from the storage device (eg. Hard disk)        
Thereafter the OS loader takes over and continues with the loading of the operating system including the OS kernel and resident OS subsystems.
Only after all these basic activities have been completed, the system is ready to perform useful tasks. This entire process takes a significant amount of time.
For a user interested in knowing the received email count this implies a significant amount of time spent in waiting for the system to actually perform the required task, from the time he/she switches it on.
Many users, especially those traveling frequently, need to keep in constant touch with their incoming mail. This requires frequent accessing of the email system. As each time the system has to be turned on, the waiting time to get email information becomes significant.